The present invention relates to a power spring drive apparatus preferably used for a toy and the like.
In a power spring of a power spring drive apparatus of the type which uses the releasing force of the wound power spring, the inner end is fastened to a wind up shaft of the power spring, and the outer end is fastened to a fastening member. Power spring driving apparatus can be categorized according to the connecting method of the outer end to the fastening member, in the following categories:
Example 1--A small type power spring motor wherein the outer end is bent in a U shape and it is fastened to a fastening member such as a pin;
Example 2--A pull back motor wherein a concave section facing the peripheral wall of the power spring housing section and a protruded section disposed at the outer end of the power spring is fastened with the concave section; the second example is mounted in a toy known by the trade name "CHORO Q";
Example 3--A KAORI box which is known as a drive source for a music box, wherein a lug section formed at the outer end fastened with a metal frame.
Regardless of the fastening method is used, to effectively use the torque of the power spring which is wound up by turning the power spring wind up shaft, it is necessary to fasten the outer end of the power spring.
In each of the first and second examples described above, the outer end of the power spring is bent, thereby raising the production cost of the entire power spring. In the first example, when winding the power spring about the power spring wind up shaft so that it is housed in the power spring housing section, unless the outer end is properly fastened to the fastening pin, since the outer end is caught in the housing section, the outer end cannot be secured.
In the second example, since the fastening section at the outer end is formed on the periphery of the power spring housing section, the size of the power spring housing box becomes large. In the third example, since the frame is made of metal, it is impossible to accomplish an accurate casing structure. In this example, to support the gear train, complicated shaped parts should be used and thereby the production cost rises.
In addition, to reduce the weight and the number of parts of the apparatus and lower the production cost, a casing made of synthetic resin is advantageous. However, for the apparatus to obtain a large driving force from the power spring, the casing tends to get damaged and deformed.